349 Intersection of Two Arrays

Given two arrays, write a function to compute their intersection.
Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2].
Note: Each element in the result must be unique. The result can be in any order.
The Idea: The intersection of two arrays are the elements they have in common.
Complexity: O(N) time and space
vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
unordered_set<int> s(nums2.begin(), nums2.end());
vector<int> intersect;
for (auto i : nums1) {
if (s.find(i) != s.end()) {
return intersect;
class Solution:
def intersection(self, nums1, nums2):
:type nums1: List[int]
:type nums2: List[int]
:rtype: List[int]
if not nums1 or not nums2:
return []
return list(set(nums1) & set(nums2))